001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2025 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018///////////////////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.checks;
021
022import java.io.File;
023import java.io.IOException;
024import java.io.RandomAccessFile;
025import java.util.Locale;
026
027import com.puppycrawl.tools.checkstyle.StatelessCheck;
028import com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck;
029import com.puppycrawl.tools.checkstyle.api.FileText;
030
031/**
032 * <div>
033 * Checks whether files end with a line separator.
034 * </div>
035 *
036 * <p>
037 * Rationale: Any not empty source files and text files in general should end with a line
038 * separator to let other easily add new content at the end of file and "diff"
039 * command does not show previous lines as changed.
040 * </p>
041 *
042 * <p>
043 * Example (the line with 'No newline at end of file' should not be in the diff):
044 * </p>
045 * <div class="wrapper"><pre class="prettyprint"><code class="language-text">
046 * &#64;&#64; -32,4 +32,5 &#64;&#64; ForbidWildcardAsReturnTypeCheck.returnTypeClassNamesIgnoreRegex
047 * PublicReferenceToPrivateTypeCheck.name = Public Reference To Private Type
048 *
049 * StaticMethodCandidateCheck.name = Static Method Candidate
050 * -StaticMethodCandidateCheck.desc = Checks whether private methods should be declared as static.
051 * \ No newline at end of file
052 * +StaticMethodCandidateCheck.desc = Checks whether private methods should be declared as static.
053 * +StaticMethodCandidateCheck.skippedMethods = Method names to skip during the check.
054 * </code></pre></div>
055 *
056 * <p>
057 * It can also trick the VCS to report the wrong owner for such lines.
058 * An engineer who has added nothing but a newline character becomes the last
059 * known author for the entire line. As a result, a mate can ask him a question
060 * to which he will not give the correct answer.
061 * </p>
062 *
063 * <p>
064 * Old Rationale: CVS source control management systems will even print
065 * a warning when it encounters a file that doesn't end with a line separator.
066 * </p>
067 *
068 * <p>
069 * Attention: property fileExtensions works with files that are passed by similar
070 * property for at <a href="https://checkstyle.org/config.html#Checker">Checker</a>.
071 * Please make sure required file extensions are mentioned at Checker's fileExtensions property.
072 * </p>
073 *
074 * <p>
075 * Notes:
076 * This will check against the platform-specific default line separator.
077 * </p>
078 *
079 * <p>
080 * It is also possible to enforce the use of a specific line-separator across
081 * platforms, with the {@code lineSeparator} property.
082 * </p>
083 *
084 * @since 3.1
085 */
086@StatelessCheck
087public class NewlineAtEndOfFileCheck
088    extends AbstractFileSetCheck {
089
090    /**
091     * A key is pointing to the warning message text in "messages.properties"
092     * file.
093     */
094    public static final String MSG_KEY_UNABLE_OPEN = "unable.open";
095
096    /**
097     * A key is pointing to the warning message text in "messages.properties"
098     * file.
099     */
100    public static final String MSG_KEY_NO_NEWLINE_EOF = "noNewlineAtEOF";
101
102    /**
103     * A key is pointing to the warning message text in "messages.properties"
104     * file.
105     */
106    public static final String MSG_KEY_WRONG_ENDING = "wrong.line.end";
107
108    /** Specify the type of line separator. */
109    private LineSeparatorOption lineSeparator = LineSeparatorOption.LF_CR_CRLF;
110
111    @Override
112    protected void processFiltered(File file, FileText fileText) {
113        try {
114            readAndCheckFile(file);
115        }
116        catch (final IOException ignored) {
117            log(1, MSG_KEY_UNABLE_OPEN, file.getPath());
118        }
119    }
120
121    /**
122     * Setter to specify the type of line separator.
123     *
124     * @param lineSeparatorParam The line separator to set
125     * @throws IllegalArgumentException If the specified line separator is not
126     *         one of 'crlf', 'lf', 'cr', 'lf_cr_crlf' or 'system'
127     * @since 3.1
128     */
129    public void setLineSeparator(String lineSeparatorParam) {
130        lineSeparator =
131            Enum.valueOf(LineSeparatorOption.class, lineSeparatorParam.trim()
132                .toUpperCase(Locale.ENGLISH));
133    }
134
135    /**
136     * Reads the file provided and checks line separators.
137     *
138     * @param file the file to be processed
139     * @throws IOException When an IO error occurred while reading from the
140     *         file provided
141     */
142    private void readAndCheckFile(File file) throws IOException {
143        // Cannot use lines as the line separators have been removed!
144        try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r")) {
145            if (lineSeparator == LineSeparatorOption.LF
146                    && endsWithNewline(randomAccessFile, LineSeparatorOption.CRLF)) {
147                log(1, MSG_KEY_WRONG_ENDING);
148            }
149            else if (!endsWithNewline(randomAccessFile, lineSeparator)) {
150                log(1, MSG_KEY_NO_NEWLINE_EOF);
151            }
152        }
153    }
154
155    /**
156     * Checks whether the content provided by the Reader ends with the platform
157     * specific line separator.
158     *
159     * @param file The reader for the content to check
160     * @param separator The line separator
161     * @return boolean Whether the content ends with a line separator
162     * @throws IOException When an IO error occurred while reading from the
163     *         provided reader
164     */
165    private static boolean endsWithNewline(RandomAccessFile file, LineSeparatorOption separator)
166            throws IOException {
167        final boolean result;
168        final int len = separator.length();
169        if (file.length() == 0) {
170            result = true;
171        }
172        else if (file.length() < len) {
173            result = false;
174        }
175        else {
176            file.seek(file.length() - len);
177            final byte[] lastBytes = new byte[len];
178            final int readBytes = file.read(lastBytes);
179            if (readBytes != len) {
180                throw new IOException("Unable to read " + len + " bytes, got "
181                        + readBytes);
182            }
183            result = separator.matches(lastBytes);
184        }
185        return result;
186    }
187
188}